Pyrimidines. XIX. Pyrimido[4,5-e]dihydro-1,3-oxazines and related compounds

A number of 2-substituted 4,5-dihydroxy-6-(substituted aminomethyl)pyrimidines (VIII) were prepared from the corresponding 2-substituted 4,5-dihydroxypyrimidines (VII) by a new pyrimidine Mannich reaction. The structure of VIII was proved by an independent synthesis. Further study of this reaction led to the synthesis of a new class of compounds: the pyrimido[4,5-e]dihydro-1,3-oxazines (VI).     

Pyrimidines. XVII. I-(Tetrahydro-2-pyranyl)cytosine, -uracil, -thymine and related compounds

In view of the reported biological activities of antibiotics Amicetin and Blasticidin S, 1-(tetrahydro-2-pyranyl)cytosine, -uracil, -thymine and related compounds were synthesized. These compounds were prepared by the Hilbert-Johnson method from 2-chloro-tetrahydropyran and corresponding 2,4-dimethoxypyrimidines.     

Streptonigrin and related compounds. 6. Synthesis and activity of some quinoxaline analogues

Streptonigrin is an antitumor antibiotic with significant in vitro and in vivo antitumor activity spectrum. Besides the total syntheses, numerous syntheses of the partial structures have been carried out in order to assess the structural requirements for the activity. The present publication deals with the synthesis of selected quinoxalinequinones to study the effect of changes in the B-ring of streptonigrin. A convenient 3-step synthesis of the required quinoxaline starting material that provides the necessary control of the desired substituent pattern is described. A series of 7-amino-6-methoxy-quinoxalinequinones were prepared in which substitution at 3- was varied (from H to Cl, OCH₃, CN, COOCH₃ and OH). A few selected 6-aminoquinones (with 6-NH₂ and 6-piperidinyl) were also prepared for comparison. The quinones (18) were tested in three different in vitro test systems: cytotoxicity to mouse leukemia (L-1210) cells, antibacterial activity against Bacillus subtilis and inhibition of root growth. Several of the aminoquinones showed significant activity in comparison to that shown by streptonigrin.     

Di-isophorone and related compounds. Part 6. The action of nucleophiles on 8-bromodi-isophorone

Hydrolysis and acetolysis of 8-bromo-1-hydroxydi-isophor-2(7)-en-3-one yields both epimeric forms of the corresponding 4-hydroxy and 4-acetoxy-compounds, probably by a mechanism involving a bimolecular (SN2) displacement. The action of excess of hydrazine on the same reactant occurs with evolution of ammonia, to produce good yields of 4-hydrazono-1-hydroxydi-isophor-2(7)-en-3-one. This is convertible into N- and O-acyl derivatives, but its 3-oxo-group fails to raact with the usual ketonic reagents. Instead, its 4-hydrazono-group is displaced by substituted hydrazines and semicarbazides in an exchange process (transhydrazination).Part 5:A. A. Allen, F. Kurzer, andA. R. Morgan, J. C. S. Perkin I1980, 733.     

Potential DNA bis-intercalating agents. Bridged bis-(6-chloropurines) and related compounds

Two bis-(6-chloropurines) bridged by conformationally restricted tethers were synthesized as potential DNA bis-intercalating agents. Reduction of 4,6-dichloro-5-nitropyrimidine ( 1 ) afforded 5-amino-4,6-dichloropyrimidine ( 2 ) which was then used as the starting material. Reaction of 2 with 4,4′-diaminodiphenylmethane ( 3 ) and bis-(4-aminophenyl) ether ( 4 ) yielded bis-[4-(N-5-amino-4-chloro-6-pyrimidyl)aminophenyl]methane ( 5 ) and bis-[4-(N-5-amino-4-chloro-6-pyrimidyl)aminophenyl] ether ( 6 ), respectively. Acid-catalyzed condensation of the above pyrimidines, 5 and 6 , with triethyl orthoformate in N,N-dimethylacetamide gave bis-[4-(6-chloro-9-purinyl)phenyl]methane ( 7 ) and bis-[4-(6-chloro-9-purinyl)phenyl] ether ( 8 ). The spectral data on the new compounds will be discussed.     

Benzomorphan related compounds. XVII . Oxidative cyclization of N-arylethyl-6, 7-benzomorphans

The synthesis of two new bridged polycyclic systems (I and II), possessing a rigid N-arylethylbenzomorphan structure, by mercuric acetate cyclization of the corresponding seco derivatives (IV and VI, respectively) is described. The relative configuration of these compounds and the preferred indolo[2, 3-a]- or benzo[a]quin-olizidine conformation is assigned.     

Picrylamino-substituted heterocycles. VI. Pyrimidines

The condensation of various aminopyrimidines with picryl chloride and picryl fluoride has been investigated as part of our continuing effort in the field of picrylamino-substituted heterocycles. Most of the aminopyrimidines that can tautomerize reacted with picryl fluoride to form picryl derivatives of their imino forms, but they gave picrylamino derivatives when they condensed with picryl chloride.     

Pyrimidines. 9. Chlorination of 6-trifluoromethyluracil with phosphorus oxychloride in the presence of trialkylamines

Ring-chlorination of 6-trifluoromethyluracil in phosphorus oxychloride in the presence of triethyl, tri-n-propyl, and tri-n-butylamines was studied with respect to by-product formation. Comparisons were made with the results obtained by treating the preformed chlorinated pyrimidine with triethyl amine in boiling toluene. Amination of chloropyrimidines by tertiary amines takes place by a Hofmann type reaction with substituent orientation generally in the 2 position of the ring. Yields of products depended on the base and reaction time. The rate of substitution in the 2 position is significantly enhanced by the presence of the trifluoromethyl group in the 6 position as compared with a methyl group. Heating preformed chloropyrimidines with tertiary amines in toluene, offers a satisfactory approach for the preparation of 2-N,N-disubstituted aminopyrimidines. For the formation of ring-chlorinated pyrimidines in phosphorus oxychloride with a minimum of by-products, tri-n-propylamine, after a short reflux period is most useful.     

Pyrimidines. 73. Synthesis of acetylpyrimidines

It is shown that the use of benzene as the solvent in the preparation of 2- and 4-acetylpyrimidines from cyanopyrimidines via the Grignard reaction makes this reaction a practical method for the preparation of pyrimidinyl ketones. Preparatively convenient methods for the preparation of 4-acetylpyrimidine from 4-ethylpyrimidine through the -oximino derivative and 5-acetylpyrimidine from 4,6-dichloro derivatives of pyrimidine are proposed.See [1] for communication 72.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 958–962, July, 1981.     

Pyrimidines. 8. chlorination of 6-methyluracil with phosphorus oxychloride in the presence of trialkyamines

The effect of the tertiary amines triethyl, tri-n-propyl, and tri-n-butylamines on the chlorination of 6-methyluracil by phosphorus oxychloride was studied. A comparison with the reaction of preformed 2,4-dichloro-6-methylpyrimidine and triethylamine in toluene was made. The reaction in phosphorus oxychloride in the presence of triethylamine afforded low yields of 2-diethylamino derivative after short heating periods and high yields of the 2,4-bis(diethylamino) derivative after 188 hours of boiling. Heating the preformed 2,4-dichloro-6-methylpyrimidine in toluene in the presence of triethylamine yielded primarily the 2-diethylaminopyrimidine along with a small amount of the 4-diethylamino isomer. After 188 hours, the product mixture was composed of 87% 2-diethylamino and 13% of 4-diethylamino isomers. Although substituent orientation was essentially the same, the yields of products seem to have been influenced by the dielectric constants of the solvents. Tri-n-propylamine in phosphorus oxychloride yielded solely the dichloropyrimidine, even after 188 hours of boiling, and is recommended as the amine of choice in such chlorination reactions. Tri-n-butylamine was the same after 48 hours, but 4% of 4-di-n-butylaminopyrimidine was found after 188 hours of heating.     

Benzoxazines and related compounds

The reaction of 2-mercapto(and benzylthio)-α,α-dialkylbenzyl alcohols with nitriles under the influence of acids serves as a method for the synthesis of 2,4,4-trisubstituted 4H-1,3-benzothiazines.     

Hydroacridines and related compounds

2-Phenyl-7,7-dimethyl-5H-7,8-dihydropyrano[4,3-b]pyridine and its N-oxide were synthesized. Refluxing of the latter with acetic anhydride gives 2-phenyl-7,7-dimethyl-8-hydroxy-5H-7,8-dihydropyrano[4,3-b]pyridine acetate; hydrolysis of the acetate gives the alcohol.See [1] for communication XII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 824–825, June, 1973.